⚡Electrical & Utility Applications
Monthly Energy Usage Analysis
Calculate utility bills: 850 kWh × $0.12/kWh = $102 monthly cost, equivalent to 3,060 MJ of energy consumption
Appliance Energy Costs
Air conditioner using 3 kW for 8 hours daily consumes 720 kWh monthly, costing $86.40
LED vs Incandescent Savings
10 LED bulbs save 2.5 kWh daily vs incandescent, resulting in $9 monthly savings
Solar Panel Output
5 kW solar system generates 750 kWh monthly (2,700 MJ), saving $90 in electricity costs
🍎Nutrition & Food Energy
Daily Caloric Requirements
Adult male needs 2,500 kcal/day = 10.46 MJ/day, equivalent to 122W continuous power consumption
Exercise Energy Expenditure
Running burns 600 kcal/hour (2,510 kJ/hr), equivalent to 697W power output during activity
Macronutrient Energy Content
Carbs & protein: 4 kcal/g (16.7 kJ/g), Fat: 9 kcal/g (37.7 kJ/g), Alcohol: 7 kcal/g (29.3 kJ/g)
Meal Planning Energy
Daily meals totaling 2,500 kcal = 10.4 MJ distributed across breakfast, lunch, dinner, and snacks
🏠HVAC & Building Energy Systems
Gas Furnace Efficiency
1,000 ft³ natural gas at 90% efficiency provides 273.5 kWh equivalent heat output
Heat Pump COP Analysis
Heat pump with COP 3.5 delivers 17.5 kW heat output from 5 kW electrical input, 3.5× more efficient than gas
Air Conditioner Load Calculation
36,000 BTU/hr cooling (3 tons) consumes ~3.5 kW, costing $3.36 daily for 8-hour operation
Building Heat Gain
Commercial office at 10 W/ft² load requires 14.2 tons of cooling capacity for 5,000 ft² space
🔧Engineering & Industrial Applications
Motor Energy Consumption
50 HP motor at 85% efficiency uses 43.9 kW input power, consuming 439 kWh daily (1,580 MJ)
Compressed Air Systems
100 CFM compressor at 125 psi uses ~22 kW, costing $422 monthly in electrical energy
Steam Generation
Industrial boiler producing 1,000 lb/hr steam at 80% efficiency requires 366 kW equivalent power input
Electric Arc Furnace
Steel melting requires 500 kWh/ton; 50-ton batch costs $1,500 in electrical energy at $0.06/kWh
❌Common Conversion Mistakes
Food vs Scientific Calories
Food 'Calories' (capital C) = kilocalories = 1,000 scientific calories. Always check units on nutrition labels
Power vs Energy Confusion
Power (W, kW) is rate; Energy (J, kWh) is total amount. A 1500W heater uses 36 kWh/day, not 1500 kWh
Ignoring System Efficiency
Real systems have losses. Output = Input × Efficiency (always <100%) due to heat, friction, resistance